The kubectl scale command is used to expand or shrink pod when the load increases or shrinks. Let’s look at some practical examples to see what the scale command can achieve.

Create a deployment command line:

Kubectl run jerry - nginx - image = nginx: 1.12.2Copy the code

Kubectl get deploy check the deployment that you just created:

Pod automatically created by Deployment:

kubectl get pod:

Use the following command to view the generated Deployment details:

kubectl get deployment jerry-nginx -o yamlCopy the code

apiVersion: extensions/v1beta1

kind: Deployment

metadata:

annotations:

deployment.kubernetes.io/revision: "1"Copy the code

creationTimestamp: 2018-11-29T08:29:06Z

generation: 1

labels:

run: jerry-nginxCopy the code

name: jerry-nginx

namespace: part-0110

resourceVersion: “7203445”

selfLink: /apis/extensions/v1beta1/namespaces/part-0110/deployments/jerry-nginx

uid: d5c64f72-f3b0-11e8-b308-a20cb743f347

spec:

progressDeadlineSeconds: 600

replicas: 1

revisionHistoryLimit: 2

selector:

matchLabels:
  run: jerry-nginxCopy the code

strategy:

rollingUpdate:
  maxSurge: 25%
  maxUnavailable: 25%
type: RollingUpdateCopy the code

template:

Metadata: creationTimestamp: NULL labels: run: jerry-nginx spec: containers: -image: nginx:1.12.2 imagePullPolicy: IfNotPresent name: jerry-nginx resources: {} terminationMessagePath: /dev/termination-log terminationMessagePolicy: File dnsPolicy: ClusterFirst restartPolicy: Always schedulerName: default-scheduler securityContext: {} terminationGracePeriodSeconds: 30Copy the code

status:

availableReplicas: 1

conditions:

  • lastTransitionTime: 2018-11-29T08:29:07Z

    lastUpdateTime: 2018-11-29T08:29:07Z

    message: Deployment has minimum availability.

    reason: MinimumReplicasAvailable

    status: “True”

    type: Available
  • lastTransitionTime: 2018-11-29T08:29:06Z

    lastUpdateTime: 2018-11-29T08:29:07Z

    message: ReplicaSet “jerry-nginx-69fd9f6c4” has successfully progressed.

    reason: NewReplicaSetAvailable

    status: “True”

    type: Progressing

    observedGeneration: 1

readyReplicas: 1

replicas: 1

updatedReplicas: 1

Another useful command:

kubectl describe deployment jerry-nginxCopy the code

Name: jerry-nginx

Namespace: part-0110

CreationTimestamp: Thu, 29 Nov 2018 16:29:06 +0800

Labels: run=jerry-nginx

Annotations: deployment.kubernetes.io/revision: 1

Selector: run=jerry-nginx

Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable

StrategyType: RollingUpdate

MinReadySeconds: 0

RollingUpdateStrategy: 25% max unavailable, 25% max surge

Pod Template:

Labels: run=jerry-nginx

Containers:

jerry-nginx:

Image: nginx:1.12.2 Port: <none> Host Port: <none> Environment: <none> Mounts: <none> MountsCopy the code

Volumes:

Conditions:

Type Status Reason

—- —— ——

Available True MinimumReplicasAvailable

Progressing True NewReplicaSetAvailable

OldReplicaSets:

NewReplicaSet: jerry-nginx-69fd9f6c4 (1/1 replicas created)

Events:

Type Reason Age From Message

—- —— —- —- ——-

Normal ScalingReplicaSet 9m41s deployment-controller Scaled up replica set jerry-nginx-69fd9f6c4 to 1

Now we scale deployment horizontally with the following command:

kubectl scale deployment jerry-nginx --replicas=3Copy the code

kubectl get pods -l run=jerry-nginxCopy the code

The Age in the figure below is 15 minutes old and was generated when the deployment was first created, and the other two ages are 1 minute old and created automatically after the scale command was executed.

Select a newly created POD and view its event log:

kubectl describe pod jerry-nginx-69fd9f6c4-8dpvbCopy the code

kubectl get replicasetCopy the code

Get the automatically created replication set:

Desired = 3 means that we specify parameter 3 when we extend horizontally.

Even if a POD instance is manually deleted, the Replication set will soon automatically create a new one:

New pods automatically created:

This article is from “Wang Zixi”, a partner of the cloud habitat community. For relevant information, you can follow the wechat public account “Wang Zixi”.